The present invention relates to an expansion jointing material for placing concrete, mortar or the like which is capable of fully absorbing or compensating for the expansion or contraction of the deposited concrete, mortar or the like, is easily and positively settable in any place or position and is capable of easily producing smooth laid surfaces of concrete or the like.
Jointing material is an indispensable material in applications where concrete, mortar or the like is used, and a variety of jointing materials have been extensively used in offices, schools, apartment houses, factories, warehouses, parking places, platforms, underground markets, roads and other rooftops, floors, walls and roads surfaces.
CONCRETE OR MORTAR USUALLY EXPANDS OR CONTRACTS AT A RATE OF 10.sup..sup.-5 PER 1.degree. C and has a tensile stress of about 20 Kg/cm and Young's modulus of between 200,000 to 280,000 Kg/cm. Therefore, if, for example, any laid rooftop of concrete or mortar is subjected to a temperature of 60.degree. C in midsummer, the resulting expansion or contraction amounts to as much as 200,000 Kg/cm .times. 10.sup..sup.-5 .times. 40.degree. C and this cannot be withstood by any means with the tensile stress of 20 Kg/cm thus causing strains or cracks. To overcome this problem, jointing material is used. While the known jointing materials have been primarily developed for the purposes of compensating for the expansion or contraction of concrete or mortar, there has still existed a need for an improved jointing material which has an improved expansion or contraction absorbing ability and which can be easily and positively installed or laid.
However, the conventional jointing materials are disadvantageous in that their ability of absorbing expansion or contraction is generally insufficient and those having a good absorbability have disadvantages of being inconvenient in handling and requiring much time and labor in laying them. For instance, while rubber jointing material has a good absorbability, it has disadvantages of being inferior in setting property, requiring much time and labor in setting, and requiring, even if it is set, an additional means to provide the required "reference" for smoothing a freshly laid surface of concrete since the material tends to be deformed by the deposited concrete. On the other hand, asphalt jointing material is also inferior in absorbing ability and is really unhandy and inefficient since its setting requires preliminary steps, namely, after preliminarily placing concrete with the aid of forms, the forms are removed from the thus laid surfaces of concrete and then the asphalt jointing material is inserted into each of the resulting grooves. One further inconvenience is that the provision of the reference requires the use of a leveling string which is stretched at every corner or the use of a plurality of studs which are projected from the laid surfaces and a vertically movable member such as a nut which is fitted on each stud to adjust the height of the stud and support between the nuts a plate for providing the required reference. As a result, to place concrete, mortar or the like over a considerably large area requires much time and labor and the resulting finished surfaces tend to produce irregularities despite the use of much time and labor. Thus, there has existed a long felt need for overcoming the foregoing deficiencies.